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Simultaneous crank-angle-resolved measurements of gasoline concentration and gas temperature were made with two-color mid-infrared (mid-IR) laser absorption in a production spark-ignition engine (Nissan MR20DE, 2.0L, 4 cyl, MPI with premium gasoline). The mid-IR light was coupled into and out of the cylinder using fiber optics incorporated into a modified spark plug. The absorption line-of-sight was a 5.3 mm optical path located closely adjacent to the ignition spark providing spatially resolved absorption. Two sensor wavelengths were selected in the strong bands associated with the carbon-hydrogen (C-H) stretching vibration near 3.4 μm, which have an absorption ratio that is strongly temperature dependent. Fuel concentration and temperature were determined simultaneously from the absorption at these two wavelengths.

NH3 and CO2 concentration measurements performed on a Biological Water Processor (BWP), under development at NASA-JSC for water recycling, using near infrared laser diode absorption spectroscopy are reported. The gaseous effluents from the bioreactor are a concern for potentially introducing harmful amounts of NH3 in a spacecraft environment. Furthermore, NH3 and CO2 monitoring is important for understanding the nitrogen and total organic carbon (TOC) balance and conversion dynamics in the BWP, and real time continuous monitoring could reveal dynamic situations that are hard to detect otherwise. Diode lasers operating at wavelengths that access NH3 and CO2 absorption lines near 1.53 μm and 1.99 μm are used in a portable and automated gas sensor system. Concentration measurements were performed during a 16 day period starting in August 25, 2000, and a 5 day period starting in November 10, 2000.

Tracer-based PLIF temperature diagnostics have been used to study the distribution and evolution of naturally occurring thermal stratification (TS) in an HCCI engine under fired and motored operation. PLIF measurements, performed with two excitation wavelengths (277, 308 nm) and 3-pentanone as a tracer, allowed investigation of TS development under relevant fired conditions. Two-line PLIF measurements of temperature and composition were first performed to track the mixing of the fresh charge and hot residuals during intake and early compression strokes. Results showed that mixing occurs rapidly with no measureable mixture stratification remaining by early compression (220°CA aTDC), confirming that the residual mixing is not a leading cause of thermal stratification for low-residual (4-6%) engines with conventional valve timing.